As a disk device, for example, a magnetic disk drive comprises a magnetic disk provided in a case, a spindle motor configured to support and rotate the magnetic disk and a magnetic head configured to read/write data from/to the magnetic disk. The magnetic head includes a recording head for writing and a read head for reading.
In recent years, the magnetic head for vertical magnetic recording has been proposed to increase the recording density and capacity of the magnetic disk drive, or to achieve miniaturization of the device. In such the magnetic head, the recording head includes a main pole which produces a magnetic field perpendicular to a recording surface of the magnetic disk and a write-shield magnetic pole placed to oppose to the main pole via a write gap. Further, for suppression of the degradation of recorded data due to the return magnetic field from the main pole, a head in which both width sides of the main pole are provided with side shields has been proposed.
It is expected that the recording head with such side shields, which can suppress magnetic field leakage in the width direction from the main pole, will be able to prevent the increase in erase width. However, in some cases, the magnetic flux in the main pole, a recording layer of the magnetic disk, and the side shield affects part of the magnetization in the side shield to be directed perpendicular to the recording layer. As a result, when recording is repeatedly carried out on the same tracks, the following drawback may occur. That is, the magnetic field produced from directly beneath the side shield, which has a width covering several tens of tracks, sometimes undesirably erase or degrade data recorded in a wide region over these tracks.